Senior .NET Framework Developer

Project overview

We are looking for a Senior .NET Developer to join a business-critical integration project within the logistics industry.

The role combines maintaining and stabilising the existing solution with helping the organisation modernise its integration architecture.

This is not a maintenance-only position. You will have the opportunity to analyse the current platform at an architectural level, influence its future direction, and support the transition from.NET Framework and WCF-based integrations to modern .NET and REST APIs.

Work Mode: hybrid from Warsaw office (3 days/week)

Start of the project: ASAP

Duration of the project: till the end of 2027 (with possibility of extension)

​Job Responsibilities

Expectations

• Maintain, stabilise, and extend a business-critical application built with C# and .NET Framework
• Develop and optimise a multithreaded, timer-driven Windows Service responsible for batch import and export processes
• Analyse the existing solution, its architecture, dependencies, and data flows
• Support the modernisation and migration of the platform towards modern .NET and API-based integrations
• Maintain and gradually replace legacy WCF/SOAP services with REST APIs
• Develop and optimise Microsoft SQL Server data access, including stored procedures and Dapper-based repositories
• Troubleshoot SQL performance issues, transactions, locking, and deadlocks
• Maintain mappings between canonical data models for shipments, milestones, status events, and customs declarations
• Investigate production incidents, resolve data consistency issues, and reprocess or correct records when required
• Cooperate with business, integration, master data, and operations teams
• Support regular environment and platform updates
• Create and maintain technical and architectural documentation
• Contribute to unit and integration testing, code reviews, and continuous improvement of development standards
• Bring a system-level perspective to discussions about the current and target architecture
• At least 6 years of commercial experience in .NET development or a similar software engineering role
• Strong hands-on experience with C# and .NET Framework 4.x
• Experience developing and maintaining Windows Services
• Practical knowledge of multithreading and the Task Parallel Library
• Strong experience with Microsoft SQL Server and T-SQL
• Hands-on experience with WCF/SOAP services
• Good understanding of REST APIs and modern integration approaches
• Experience with XML, XSD schemas, XML serialization, and XSLT mappings
• Knowledge of object mapping tools such as AutoMapper
• Experience with lightweight ORMs, preferably Dapper
• Familiarity with dependency injection
• Experience with unit testing frameworks such as MSTest and mocking libraries such as Moq
• Practical knowledge of Git
• Architectural mindset and the ability to understand dependencies between applications, services, and integrations
• Willingness to work with an existing legacy codebase while actively supporting its modernisation
• Fluent English, minimum C1 level
• Polish language proficiency

Nice to have

We offer

About Darize

Some projects keep businesses running. Others help them evolve and grow. If you're more drawn to the latter, chances are we have a lot in common. At Darize, we work with organizations tackling complex technology challenges.

In IT, one challenge is always around the corner: before one project ends, it’s already time to think about the next. Add uncertainty, rate negotiations, and administrative tasks, and it’s easy to lose focus on what matters most. That’s why we do more than connect experts with projects. We provide stability, access to ambitious technology initiatives, and a community of experienced professionals, so you can focus on what you do best.

Darize brings together more than 2,500 consultants across 24 countries. In Poland, you may know us as 7N, the brand we built for over 20 years. We value expertise, long-term relationships, and a culture rooted in trust, quality, and Nordic values. We challenge the status quo and create an environment where people matter more than processes.

• Experience migrating applications from.NET Framework to modern .NET, including .NET 8+
• Knowledge of freight forwarding or logistics processes, including shipments, transport stages, and status events
• Experience with Microsoft Azure, particularly Azure Functions or App Services
• Familiarity with Docker and Kubernetes
• Understanding of enterprise integration or ESB environments
• Experience working in Agile or Scrum teams
• Dedicated Agent support – your go-to person for project continuity, client communication, day-to-day administration, and long-term professional development
• Access to Darize Learning & Development – our internal development platform featuring webinars, industry reports and articles, access to learning platforms such as DataCamp and Coursera, and regular invitations to technical, business, and lifestyle events
• Community and networking events – from Kick-Off trips, Christmas celebrations, and Summer Sport Games to family picnics and cultural events for you and your loved ones
• Consultant Development Program – personalized professional development support based on current industry trends and market needs, delivered by experienced mentors and development advisors
• Comprehensive benefits package – including private healthcare, life insurance, a sports card for you and your family members, as well as access to employee discounts in Poland and abroad
• A community of experienced IT experts – exchange knowledge and collaborate with technology professionals who bring years of hands-on experience delivering complex technology projects (the average professional experience of our consultants in Poland exceeds 10 years)

Project details

• Start: flexible
• Location: Warsaw, Poland, PL
• Rate: 135-145 EUR/h